Topical Gels and Methods of Using the Same

ABSTRACT

Provided according to some embodiments of the invention are topical gels that may release nitric oxide. Also provided are methods of using such topical gels in the treatment of wounds and other skin ailments. The topical gels comprise diazeniutndiolate-functionalized polysiloxane macromolecules.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority from U.S. Provisional Application Ser. No. 61/235,933, filed Aug. 21, 2009, the disclosure of which is hereby incorporated by reference herein in its entirety.

FIELD OF THE INVENTION

The present invention relates to topical gels that may controllably release nitric oxide. The present invention also relates to methods of using topical gels that may controllably release nitric oxide.

BACKGROUND OF THE INVENTION

Skin has a myriad of functions, including protection against pathogens and excessive water loss, insulation, temperature regulation, sensation and protection of vitamin B folates. As such, impairment or ailments of the skin may significantly affect the health of a person or animal. Furthermore, such impairments or ailments may cause irritation, pain or other discomfort and may undesirably affect the person or animal's physical appearance.

An important aspect for the treatment of many skin impairments or ailments, including wounds and burns, is the control of infection, which may facilitate the healing process. Topical medicaments are commonly used tools to protect wounds and other skin ailments from infection. Antimicrobial agents are often incorporated into topical medicaments and wound dressing to treat and prevent infection. However, there may be disadvantages associated with use of antimicrobial agents. It has been observed that an increasing number of pathogens have developed resistance to conventional antibiotic treatments. According to statistics, antibiotic-resistant pathogens are the primary reason for a majority of all lethal nosocomial infections. See Robson et al., Surg. Clin. N. Am. 77, 637-650 (1977). Furthermore, many antimicrobial agents not only kill pathogens, but also impose a threat to the proliferating granulation tissue, fibroblasts and keratinocytes that may help with the wound healing process. Additionally, some antimicrobial agents may cause allergic reactions in some patients.

It is known that nitric oxide possesses a broad-spectrum of antimicrobial activity and may be used as an alternative to conventional antibiotics for drug resistant bacteria. Furthermore, some recent studies have demonstrated that nitric oxide may also play an important role in the wound healing process by promoting angiogenesis through stimulation of vascular endothelial growth factor (VEGF) and increase fibroblast collagen synthesis. See Schaffer M R, et al., Diabetes-impaired healing and reduced wound nitric oxide synthesis: A possible pathophysiologic correlation. Surgery 1997; 121(5):513-9; and Shi H P, et al., The role of iNOS in wound healing. Surgery 2001; 130 (2):225-9. Thus, nitric oxide presents a promising addition and/or alternative to the conventional antibiotic treatments. Furthermore, nitric oxide has been shown to have other beneficial properties, including reducing inflammation and participation in wound healing biochemical cascades. Unfortunately, the relationship between exogenously applied concentrations of nitric to promote healing, mediate inflammation, or treat infection are not clearly understood.

Nitric oxide is a gas at ambient temperature and atmospheric pressure, and it has a short half-life in a physiological milieu. Several small molecule nitric oxide donor prodrugs have been developed which have contributed greatly to the understanding of nitric oxide in a number of disease states. However, due to their issues with stability, indiscriminate NO-release, monotypical nitric oxide release kinetics, and inability to target specific tissue types, optimal solutions for administering nitric oxide outside of its gaseous form have not yet been achieved. Reproducibly delivering the correct levels of nitric oxide for a given therapeutic indication is critical because the release of large amounts of nitric oxide may be toxic or create undesirable side effects such as an increase in inflammation. Therefore, it has been challenging to use nitric oxide for topical therapeutic applications, particularly for reproducibly delivering nitric oxide in a controlled manner from vehicles capable of targeting tissue structures.

As an example, previous investigators have explored the use of topical formulations containing an alkali nitrite source in combination with ascorbic acid or other organic acid, that upon admixture or mixing create a rapid bolus of nitric oxide release. While the antimicrobial efficacy of nitric oxide released via this approach has been shown, it may also result in decrease in angiogenesis, increase in inflammation and unwanted toxicity. Thus, the need exists for topical treatments and medicaments that can release nitric oxide by a controlled delivery method.

SUMMARY OF THE INVENTION

Provided according to embodiments of the invention are topical gels that release nitric oxide (NO). In some embodiments of the invention, the topical gels include diazeniumdiolate-functionalized polysiloxane macromolecules and a hydrophobic, non-aqueous gel base. In some embodiments, the hydrophobic, non-aqueous gel base is a silicone gel. Furthermore, in some embodiments, the diazeniumdiolate-functionalized polysiloxane macromolecules and gel excipients have an octanol/water partition coefficient in a range of 0.1 to 7.

In some embodiments of the invention, the topical gels include diazeniumdiolate-functionalized polysiloxane macromolecules and a hydrophilic gel base. As such, in some embodiments, the diazeniumdiolate-functionalized polysiloxane macromolecules and the gel excipients have an octanol/water partition coefficient in a range of −2 to 0.

In some embodiments of the invention, the concentration of the diazeniumdiolate-functionalized polysiloxane macromolecules in the gel is in a range of 0.1 to 20 weight %.

In some embodiments of the invention, the diazeniumdiolate-functionalized polysiloxane macromolecules have a hydrodynamic radius in a range of 1000 nm to 10 microns. In some embodiments of the invention, the diazeniumdiolate-functionalized polysiloxane macromolecules have a hydrodynamic radius in a range of 1 nm to 100 nm.

The nitric oxide storage of the gels may be tailored. In some embodiments, the nitric oxide storage per gram is in a range of 0.1 pmol NO/g to 100 nmol/g gel. In some embodiments, the nitric oxide storage per gram is in a range of 1 nmol NO/g to 10 mmol/g gel. In some embodiments, the nitric oxide storage per gram is in a range of 10 mmol NO/g to 1 mmol/g gel.

In some embodiments of the invention, the gels further include other therapeutic agents such as an anti-acne agent, antimicrobial agent, benzoyl peroxide, or a corticosteroid.

Also provided herein are methods of treating wounds that include wound comprising applying the topical gel according to an embodiment of the invention. In particular embodiments, methods include treatment of burns and treatment of acne.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate certain embodiment(s) of the invention.

FIG. 1 is a schematic for the synthesis of diazeniumdiolate-functionalized polysiloxane macromolecules according to some embodiments of the invention.

FIG. 2A is a graph illustrating the efficacy of diazeniumdiolate-functionalized polysiloxane macromolecules according to some embodiments of the invention at killing P. aeruginosa.

FIG. 2B is a graph illustrating the efficacy of diazeniumdiolate-functionalized polysiloxane macromolecules according to some embodiments of the invention at killing MRSA.

FIG. 3 is a graph illustrating the dose dependence of the efficacy of diazeniumdiolate-functionalized polysiloxane macromolecules according to some embodiments of the invention at killing P. aeruginosa.

FIG. 4 is a graph illustrating the dose dependence of diazeniumdiolate-functionalized polysiloxane macromolecules according to some embodiments of the invention on wound healing.

FIG. 5 shows a series of images of wound healing versus time for the graph in FIG. 4.

FIG. 6 provides the NO-release versus time for a gel according to an embodiment of the invention.

FIG. 7 shows NO-release curves showing change in kinetic profile as a function of excipients versus diazeniumdiolate-functionalized polysiloxane macromolecules alone.

FIG. 8 shows the NO stability in gel over time decreases as a function of gel components.

FIG. 9 shows the antimicrobial time-kill of P. aeruginosa for diazeniumdiolate-functionalized polysiloxane macromolecules vs. formulated hydrophobic gel at equivalent concentrations of silica.

FIG. 10 shows the hydrophilic vs. hydrophobic gel time kill efficacy against P. aeruginosa for particular gels according to some embodiments of the invention.

FIG. 11 shows the dose and time kill efficacy of diazeniumdiolate-functionalized polysiloxane macromolecules according to an embodiment of the invention against P. acnes.

FIG. 12 shows the dose and time kill efficacy of diazeniumdiolate-functionalized polysiloxane macromolecules according to an embodiment of the inveniton against T. rubrum.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The foregoing and other aspects of the present invention will now be described in more detail with respect to the description and methodologies provided herein. It should be appreciated that the invention can be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

The terminology used in the description of the invention herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the description of the embodiments of the invention and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. Also, as used herein, “and/or” refers to and encompasses any and all possible combinations of one or more of the associated listed items. Furthermore, the term “about,” as used herein when referring to a measurable value such as an amount of a compound, dose, time, temperature, and the like, is meant to encompass variations of 20%, 10%, 5%, 1%, 0.5%, or even 0.1% of the specified amount. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Unless otherwise defined, all terms, including technical and scientific terms used in the description, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

All patents, patent applications and publications referred to herein are incorporated by reference in their entirety. In the event of conflicting terminology, the present specification is controlling.

The embodiments described in one aspect of the present invention are not limited to the aspect described. The embodiments may also be applied to a different aspect of the invention as long as the embodiments do not prevent these aspects of the invention from operating for its intended purpose.

Chemical Definitions

As used herein the term “alkyl” refers to C₁₋₂₀ inclusive, linear (i.e., “straight-chain”), branched, or cyclic, saturated or at least partially and in some cases fully unsaturated (i.e., alkenyl and alkynyl)hydrocarbon chains, including for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, tert-butyl, pentyl, hexyl, octyl, ethenyl, propenyl, butenyl, pentenyl, hexenyl, octenyl, butadienyl, propynyl, butynyl, pentynyl, hexynyl, heptynyl, and allenyl groups. “Branched” refers to an alkyl group in which a lower alkyl group, such as methyl, ethyl or propyl, is attached to a linear alkyl chain. Exemplary branched alkyl groups include, but are not limited to, isopropyl, isobutyl, tert-butyl. “Lower alkyl” refers to an alkyl group having 1 to about 8 carbon atoms (i.e., a C₁₋₈ alkyl), e.g., 1, 2, 3, 4, 5, 6, 7, or 8 carbon atoms. “Higher alkyl” refers to an alkyl group having about 10 to about 20 carbon atoms, e.g., 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms. In certain embodiments, “alkyl” refers, in particular, to C₁₋₅ straight-chain alkyls. In other embodiments, “alkyl” refers, in particular, to C₁₋₅ branched-chain alkyls.

Alkyl groups can optionally be substituted (a “substituted alkyl”) with one or more alkyl group substituents, which can be the same or different. The term “alkyl group substituent” includes but is not limited to alkyl, substituted alkyl, halo, arylamino, acyl, hydroxyl, aryloxyl, alkoxyl, alkylthio, arylthio, aralkyloxyl, aralkylthio, carboxyl, alkoxycarbonyl, oxo, and cycloalkyl. There can be optionally inserted along the alkyl chain one or more oxygen, sulfur or substituted or unsubstituted nitrogen atoms, wherein the nitrogen substituent is hydrogen, lower alkyl (also referred to herein as “alkylaminoalkyl”), or aryl.

Thus, as used herein, the term “substituted alkyl” includes alkyl groups, as defined herein, in which one or more atoms or functional groups of the alkyl group are replaced with another atom or functional group, including for example, alkyl, substituted alkyl, halogen, aryl, substituted aryl, alkoxyl, hydroxyl, nitro, amino, alkylamino, dialkylamino, sulfate, and mercapto.

The term “aryl” is used herein to refer to an aromatic substituent that can be a single aromatic ring, or multiple aromatic rings that are fused together, linked covalently, or linked to a common group, such as, but not limited to, a methylene or ethylene moiety. The common linking group also can be a carbonyl, as in benzophenone, or oxygen, as in diphenylether, or nitrogen, as in diphenylamine. The term “aryl” specifically encompasses heterocyclic aromatic compounds. The aromatic ring(s) can comprise phenyl, naphthyl, biphenyl, diphenylether, diphenylamine and benzophenone, among others. In particular embodiments, the term “aryl” means a cyclic aromatic comprising about 5 to about 10 carbon atoms, e.g., 5, 6, 7, 8, 9, or 10 carbon atoms, and including 5- and 6-membered hydrocarbon and heterocyclic aromatic rings.

The aryl group can be optionally substituted (a “substituted aryl”) with one or more aryl group substituents, which can be the same or different, wherein “aryl group substituent” includes alkyl, substituted alkyl, aryl, substituted aryl, aralkyl, hydroxyl, alkoxyl, aryloxyl, aralkyloxyl, carboxyl, acyl, halo, nitro, alkoxycarbonyl, aryloxycarbonyl, aralkoxycarbonyl, acyloxyl, acylamino, aroylamino, carbamoyl, alkylcarbamoyl, dialkylcarbamoyl, arylthio, alkylthio, alkylene, and —NR¹R″, wherein R¹ and R″ can each be independently hydrogen, alkyl, substituted alkyl, aryl, substituted aryl, and aralkyl.

Thus, as used herein, the term “substituted aryl” includes aryl groups, as defined herein, in which one or more atoms or functional groups of the aryl group are replaced with another atom or functional group, including for example, alkyl, substituted alkyl, halogen, aryl, substituted aryl, alkoxyl, hydroxyl, nitro, amino, alkylamino, dialkylamino, sulfate, and mercapto. Specific examples of aryl groups include, but are not limited to, cyclopentadienyl, phenyl, furan, thiophene, pyrrole, pyran, pyridine, imidazole, benzimidazole, isothiazole, isoxazole, pyrazole, pyrazine, triazine, pyrimidine, quinoline, isoquinoline, indole, carbazole, and the like.

“Cyclic” and “cycloalkyl” refer to a non-aromatic mono- or multicyclic ring system of about 3 to about 10 carbon atoms, e.g., 3, 4, 5, 6, 7, 8, 9, or 10 carbon atoms. The cycloalkyl group can be optionally partially unsaturated. The cycloalkyl group also can be optionally substituted with an alkyl group substituent as defined herein, oxo, and/or alkylene. There can be optionally inserted along the cyclic alkyl chain one or more oxygen, sulfur or substituted or unsubstituted nitrogen atoms, wherein the nitrogen substituent is hydrogen, alkyl, substituted alkyl, aryl, or substituted aryl, thus providing a heterocyclic group. Representative monocyclic cycloalkyl rings include cyclopentyl, cyclohexyl, and cycloheptyl. Multicyclic cycloalkyl rings include adamantyl, octahydronaphthyl, decalin, camphor, camphane, and noradamantyl.

“Alkoxyl” refers to an alkyl-O— group wherein alkyl is as previously described. The term “alkoxyl” as used herein can refer to, for example, methoxyl, ethoxyl, propoxyl, isopropoxyl, butoxyl, f-butoxyl, and pentoxyl. The term “oxyalkyl” can be used interchangeably with “alkoxyl”. In some embodiments, the alkoxyl has 1, 2, 3, 4, or 5 carbons.

“Aralkyl” refers to an aryl-alkyl group wherein aryl and alkyl are as previously described, and included substituted aryl and substituted alkyl. Exemplary aralkyl groups include benzyl, phenylethyl, and naphthylmethyl.

“Alkylene” refers to a straight or branched bivalent aliphatic hydrocarbon group having from 1 to about 20 carbon atoms, e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 carbon atoms. The alkylene group can be straight, branched or cyclic. The alkylene group also can be optionally unsaturated and/or substituted with one or more “alkyl group substituents.” There can be optionally inserted along the alkylene group one or more oxygen, sulfur or substituted or unsubstituted nitrogen atoms (also referred to herein as “alkylaminoalkyl”), wherein the nitrogen substituent is alkyl as previously described. Exemplary alkylene groups include methylene (—CH₂—); ethylene (—CH₂—CH₂—); propylene (—(CH₂)₃—); cyclohexylene (—C₆H₁₀—); —CH═CH—CH═CH—; —CH═CH—CH₂—; wherein each of q and r is independently an integer from 0 to about 20, e.g., 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20, and R is hydrogen or lower alkyl; methylenedioxyl (—O—CH₂—O—); and ethylenedioxyl (—O—(CH₂)₂—O—). An alkylene group can have about 2 to about 3 carbon atoms and can further have 6-20 carbons.

“Arylene” refers to a bivalent aryl group. An exemplary arylene is phenylene, which can have ring carbon atoms available for bonding in ortho, meta, or para positions with regard to each other, i.e., respectively. The arylene group can also be napthylene. The arylene group can be optionally substituted (a “substituted arylene”) with one or more “aryl group substituents” as defined herein, which can be the same or different.

“Aralkylene” refers to a bivalent group that contains both alkyl and aryl groups. For example, aralkylene groups can have two alkyl groups and an aryl group (i.e., -alkyl-aryl-alkyl-), one alkyl group and one aryl group (i.e., -alkyl-aryl-) or two aryl groups and one alkyl group (i.e., -aryl-alkyl-aryl-).

The term “amino” and “amine” refer to nitrogen-containing groups such as NR₃, NH₃, NHR₂, and NH₂R, wherein R can be alkyl, branched alkyl, cycloalkyl, aryl, alkylene, arylene, aralkylene. Thus, “amino” as used herein can refer to a primary amine, a secondary amine, or a tertiary amine. In some embodiments, one R of an amino group can be a cation stabilized diazeniumdiolate (i.e., NONO⁻X⁺).

The terms “cationic amine” and “quaternary amine” refer to an amino group having an additional (i.e., a fourth) group, for example a hydrogen or an alkyl group bonded to the nitrogen. Thus, cationic and quartemary amines carry a positive charge.

The term “alkylamine” refers to the -alkyl-NH₂ group.

The term “carbonyl” refers to the —(C═O)— group.

The term “carboxyl” refers to the —COOH group and the term “carboxylate” refers to an anion formed from a carboxyl group, i.e., —COO⁻.

The terms “halo”, “halide”, or “halogen” as used herein refer to fluoro, chloro, bromo, and iodo groups.

The term “hydroxyl” and “hydroxy” refer to the —OH group.

The term “hydroxyalkyl” refers to an alkyl group substituted with an —OH group.

The term “mercapto” or “thio” refers to the —SH group. The term “silyl” refers to groups comprising silicon atoms (Si).

As used herein the term “alkoxysilane” refers to a compound comprising one, two, three, or four alkoxy groups bonded to a silicon atom. For example, tetraalkoxysilane refers to Si(OR)₄, wherein R is alkyl. Each alkyl group can be the same or different. An “alkylsilane” refers to an alkoxysilane wherein one or more of the alkoxy groups has been replaced with an alkyl group. Thus, an alkylsilane comprises at least one alkyl-Si bond. The term “fluorinated silane” refers to an alkylsilane wherein one of the alkyl groups is substituted with one or more fluorine atoms. The term “cationic or anionic silane” refers to an alkylsilane wherein one of the alkyl groups is further substituted with an alkyl substituent that has a positive (i.e., cationic) or a negative (i.e. anionic) charge, or can become charged (i.e., is ionizable) in a particular environment (i.e., in vivo).

The term “silanol” refers to a Si—OH group.

Provided according to some embodiments of the invention are topical medicaments that include NO-releasing macromolecules. In some embodiments, the NO-releasing macromolecules are diazeniumdiolate-functionalized polysiloxane macromolecules. Furthermore, in some embodiments, the medicaments include diazeniumdiolate-functionalized polysiloxane macromolecules in a gel.

In some embodiments of the invention, the properties of the gel are selected based on the properties of the diazeniumdiolate-functionalized polysiloxane macromolecules and the indication for which the topical gel is to be used, such that the interaction of the properties of the gel, macromolecule and skin environment act to provide the desired NO release profile. At the same time, the gel must be suitably stable and resist decomposition prior to topical application.

The Diazeniumdiolate-Functionalized Polysiloxane Macromolecules

The term “diazeniumdiolate-functionalized polysiloxane macromolecules” refers co-condensed polysiloxane macromolecules functionalized with diazeniumdiolate, such as the NO-releasing particles described in U.S. Publication No. 2009/0214618, the disclosure of which is incorporated by reference herein in its entirety. Such particles may be prepared by methods described therein.

In some embodiments, the nitric oxide donor may be formed from an aminoalkoxysilane by a pre-charging method, and the co-condensed siloxane network may be synthesized from the condensation of a silane mixture that includes an alkoxysilane and the aminoalkoxysilane to form a nitric oxide donor modified co-condensed siloxane network. As used herein, the “pre-charging method” means that aminoalkoxysilane is “pretreated” or “precharged” with nitric oxide prior to the co-condensation with alkoxysilane. In some embodiments, the precharging nitric oxide may be accomplished by chemical methods. In another embodiment, the “pre-charging” method can be used to create co-condensed siloxane networks and materials more densely functionalized with NO-donors.

The co-condensed siloxane network can be silica particles with a uniform size, a collection of silica particles with a variety of size, amorphous silica, a fumed silica, a nanocrystalline silica, ceramic silica, colloidal silica, a silica coating, a silica film, organically modified silica, mesoporous silica, silica gel, bioactive glass, or any suitable form or state of silica.

In some embodiments, the alkoxysilane is a tetraalkoxysilane having the formula Si(OR)₄, wherein R is an alkyl group. The R groups can be the same or different. In some embodiments the tetraalkoxysilane is selected as tetramethyl orthosilicate (TMOS) or tetraethyl orthosilicate (TEOS). In some embodiments, the aminoalkoxysilane has the formula: R″-(NH—R′)_(n)—Si(OR)₃, wherein R is alkyl, R′ is alkylene, branched alkylene, or aralkylene, n is 1 or 2, and R″ is selected from the group consisting of alkyl, cycloalkyl, aryl, and alkylamine.

In some embodiments, the aminoalkoxysilane can be selected from N-(6-aminohexyl)aminopropyltrimethoxysilane (AHAP3); N-(2-aminoethyl)-3-aminopropyltrimethoxysilane (AEAP3); (3-trimethoxysilylpropyl)di-ethylenetriamine (DET3); (amino ethylaminomethyl)phenethyltrimethoxysilane (AEMP3); [3-(methylamino)propyl]trimethoxysilane (MAP3); N-butylamino-propyltrimethoxysilane(n-BAP3); t-butylamino-propyltrimethoxysilane (t-BAP3); N-ethylaminoisobutyltrimethoxysilane (EAiB3); N-phenylamino-propyltrimethoxysilane (PAP3); and N-cyclohexylaminopropyltrimethoxysilane (cHAP3).

In some embodiments, the aminoalkoxysilane has the formula: NH [R′—Si(OR)₃]₂, wherein R is alkyl and R′ is alkylene. In some embodiments, the aminoalkoxysilane can be selected from bis(3-triethoxysilylpropyl)amine, bis-[3-(trimethoxysilyl)propyl]amine and bis-[(3-trimethoxysilyl)propyl]ethylenediamine.

In some embodiments, as described herein above, the aminoalkoxysilane is precharged for NO-release and the amino group is substituted by a diazeniumdiolate. Therefore, in some embodiments, the aminoalkoxysilane has the formula: R″—N(NONO⁻X⁺)—R′—Si(OR)₃, wherein R is alkyl or silyl, R′ is alkylene or aralkylene, R″ is alkyl or alkylamine, and X⁺ is a cation selected from the group consisting of Na⁺, K⁺, Cs⁺, Li⁺, NH₄ ⁺, or other quaternary ammonium cation.

In some embodiments of the invention, the diazeniumdiolate-functional aminoalkoxysilane may be O²-protected prior to the preparation of the nitric oxide releasing macromolecules. Such O²-protected diazeniumdiolate functional aminoalkoxysilanes may have the formula: R″-N(NONO—R′″)—R′—Si(OR)₃, wherein each R is independently H, alkyl or substituted alkyl, R′ is substituted or unsubstituted alkylene, substituted or unsubstituted arylene, substituted or unsubstituted alkylarylene or substituted or unsubstituted arylalkylene, R″ is H, alkyl or substituted alkyl and R′″ is a protecting group that imparts enzymatic, photolytic, or thiolation triggering mechanisms. Such protecting groups are known to those skilled in the art of forming O²-protected diazeniumdiolates.

The chemical composition of the siloxane network, (e.g., amount or the chemical composition of the aminoalkoxysilane), the porosity of the silica network within the macromolecular structure, the size of the co-condensed silica particles, and the nitric oxide charging conditions (e.g., the solvent and base) can be varied to optimize the amount and duration of nitric oxide release. Thus, in some embodiments, the composition of the silica particles can be modified to regulate the half-life of NO release from silica particles with half-lives of nitric oxide release ranging from slow, defined by t_(1/2) values greater than 60 minutes to fast, defined by t_(1/2) values ranging from 30 seconds to 10 minutes.

In some embodiments of the invention, the co-condensed siloxane network of nitric oxide releasing silica particles is formed from at least one additional silane that modifies surface charge and/or hydrophilicity/hydrophobicity of the co-condensed silica product which affect the octanol/water partition coefficient of the macromolecular delivery vehicle. These parameters control the route of skin penetration, depth of penetration, and diffusion of the diazeniumdiolate-modified polysiloxane macromolecules out of topical gel vehicles. Any suitable alkoxysilane that may impart surface charge to the diazeniumdiolate-modified polysiloxane macromolecule may be used. Thus, in some embodiments, the additional alkoxysilane may include a cationic alkoxysilane such as (2-N-benyzlaminoethyl)-3-aminopropyl-trimethoxysilane, hydrocholoride; bis(methoxyethyl)-3-trimethoxysilylpropyl-ammonium chloride; N—N-didecyl-N-methyl-N-(3-trimethoxysilyl)ammonium chloride; N-trimethyoxysilylpropyl-N,N,N-trimethyl ammonium chloride; octadecylbis(triethoxysilylpropyl)-ammonium chloride; and octadecyldimethyl(3-trimethoxysilylpropyl)ammonium chloride. In some embodiments, the additional alkoxysilane may include an anionic alkoxysilanes such as 3-trihydroxysilylpropylmethyl phosphonate, sodium salt and carboxyethylsilanetriol, sodium salt.

Any suitable alkoxysilane that may impart hydrophilic properties to the diazeniumdiolate-modified polysiloxane macromolecule may be used. Alkoxysilanes containing repeat poly(ethylene)oxy groups may be used to increase the wetability of the NO-releasing particles thereby helping to improve biocompatibility upon topical application and also enhance the rate of water uptake into the co-condensed siloxane coating. Surface hydrophilicity can thus be utilized to enhance the NO-release kinetics of the diazeniumdiolated aminoalkoxysilane derivatives. Therefore, in some embodiments, the multifunctional alkoxysilane may include a hydrophilic silane such as N-triethoxysilylpropyl)-O-polyethyleneoxide urethane; N-3-[amino(polypropylenoxy)]aminopropyltrimethoxysilane; bis-[3-(triethoxysilylpropoxy)-2-hydroxypropoxy]polyethylene oxide; bis(3-triethoxysilylpropyl)polyethylene oxide (25-30); [hydroxy(polyethyleneoxy)propyl]-triethoxysilane; and 2-[methoxy(polyethyleneoxy)propyl]-trimethoxysilane.

Any suitable alkoxysilane that may impart hydrophobic properties to the diazeniumdiolate-modified polysiloxane macromolecule may be used. Hydrophobic silanes are known to those skilled in the art to increase lipophilicity of particle surfaces. In some embodiments, the additional alkoxysilane may include linear alkyl, branched and cyclic alkylalkoxysilanes having at least three carbon atoms, substituted and unsubstituted phenyl alkoxysilanes, and fluorinated alkoxysilanes. Exemplary fluoroalkoxysilanes may include heptadecafluoro-1,1,2-2-tetrahydrodecyl)triethoxysilane (shown in FIG. 2I), (3,3,3-trifluoropropyl)trimethoxysilane, (perfluoroalkyl)ethyltriethoxysilane, nonafluorohexyltrimethoxysilane, nonafluorohexyltriethoxysilane, (tridecafluoro-1,1,2,2-tetrahydrooctyl)triethoxysilane, and (tridecafluoro-1,1,2,2-tetrahydrooctyl)trimethoxysilane.

The hydrophilicity of the diazeniumdiolate-functionalized polysiloxane macromolecules can be assessed by the use of a water/octanol partition coefficient. See Octanol-Water Partition Coefficients: Fundamentals and Physical Chemistry, Vol. 2 of Wiley Series in Solution Chemistry. Chichester: John Wiley & Sons Ltd. (1997), which is herein incorporated by reference in its entirety. For example, hydrophobic diazeniumdiolate-functionalized polysiloxane macromolecules may have a water/octanol partition coefficient in a range of 0.1 to 7, and hydrophilic diazeniumdiolate-functionalized polysiloxane macromolecules may have a water/octanol partition coefficient in a range of −2 to 0.

In some embodiments of the invention, the hydrodynamic radius of the NO-releasing macromolecule is within a range of 1 nm to 100 nm, which may maximize trans-epidermal skin penetration and enhance nitric oxide delivery to deeper skin structures or, the size of the macromolecular scaffold may be selected to be in a range of 101 nm to 1000 nm to selectively accumulate diazeniumdiolate-modified polysiloxane macromolecules in the stratum corneum and limit skin penetration, systemic absorption, and any resulting toxicity of the macromolecular scaffold, or the size of the macromolecule scaffold may be selected to be in a range of 1000 nm to 10,000 nm to target skin penetration via the trans-follicular route. Selective delivery to the stratum corneum, epidermis or dermis may be achieved by varying the particle size. Skin naturally has a low permeability to particulate materials and the stratum corneum provides an effective barrier to most inorganic nanosized particles with gold nanoparticles, silver nanoparticles, quantum dots, titanium dioxodie, and zinc oxide being the most extensively studied. See, e.g., Baroli, B., Penetration of Nanoparticles and Nanomaterials in the Skin: Fiction or Reality? Journal of Pharmaceutical Sciences, 2009 December; 99:21-50. Despite the current understanding of one skilled in the art of skin penetration, the skin penetration of silica particles as a function of size is poorly understood.

The diazeniumdiolate-functionalized polysiloxane macromolecules may be present in medicaments according to embodiments of the invention at any suitable concentration, but in some embodiments, the diazeniumdiolate-functionalized polysiloxane macromolecules are present in the medicaments at a concentration sufficient to increase the rate of wound healing, decrease inflammation and/or exert an antimicrobial effect. In particular embodiments, the concentration of diazeniumdiolate-functionalized polysiloxane macromolecules is in a range of 0.01 percent to 20 percent w/w. In some embodiments, the concentration of the diazeniumdiolate-functionalized polysiloxane macromolecules in the medicament may be adjusted to modulate the amplitude of nitric oxide release (mol NO/g medicament) either by changing the weight percentage in the gel or by varying the loading of nitric oxide on the macromolecular scaffold to create a desirable therapeutic outcome.

In some embodiments, to prevent platelet activation and aggregation, the final NO storage per gram of gel may be in a range of 0.1 pmol NO/g gel to 100 nmol/g gel. In some embodiments, to reduce inflammation and associated inflammatory response factors, the final NO storage per gram of gel may be in a range of 100 pmol NO/g gel to 1 umol NO/g gel. In some embodiments, to promote wound healing, the final NO storage per gram of gel may be in a range of 1 nmol NO/g gel to 10 μmol NO/g gel. In some embodiments, to exert antimicrobial activity, the final NO storage per gram of gel may be in a range of 10 μmol NO/g gel to 1 mmol NO/g gel. In some embodiments, to treat biofilms by dispersal, the final NO storage per gram of gel may be in a range of 10 nmol NO/g gel to 1 μmol NO/g gel, and in some embodiments, to treat biofilms by direct microbicidal activity, the final NO storage per gram of gel may be in a range of 100 μmol NO/g gel to 1 mmol NO/g gel.

Topical Gels

The properties of the topical gels, including the NO-release profile, may be tailored by the selection of the gel composition. The gels may also provide beneficial or therapeutic action to the skin or wound bed (e.g., moisturize, absorb wound exudate, provide an occlusive barrier, etc.) that may directly affect skin conditions or wound healing. The excipients that form the gels may also indirectly affect wound healing by affecting the stability of the diazeniumdiolate-functionalized polysilane macromolecules or other therapeutic agents within the medicament and/or controlling the rates of decomposition of the NO donors to generate nitric oxide. The intrinsic pH of the topical gel can be elevated to between 8 and 10 to maintain NO donor stability and react with the acid mantle on the surface of the skin to neutralize pH and initiate decomposition of diazeniumdiolate nitric oxide donors.

Excipients for use in topical gels are well-known in the art and examples may be found in the Handbook of Pharmaceutical Excipients (Rowe, R. C. et al., APhA Publications; 5^(th) ed., 2005). Exemplary excipients may include waxes, various sugars and types of starch, polymers, gels, emollients, thickening agents, rheology modifiers, humectants, glycerol, organic basic compounds, cellulose derivatives, gelatin, vegetable oils, polyethylene glycols and solvents. Examples of rheology modifiers include Carbopol, hydroxypropyl cellulose, C₂₆₋₂₈ alkyl dimethicone, C₂₆₋₂₈ alkyl methicone, polyphenylsisquioxane, trimethylsiloxysilicate, crosspolymers of cyclopentasiloxane and dimethicone/vinyltrimethylsiloxysilicate, fumed silica (e.g. Cab-O-Sil M5P), and mixtures thereof. Examples of emollients include glycerine, pentylene glycol, sodium pyrrolidone carboxylic acid, lanolin, saccharide isomerate, stearoxy dimethicone, stearyl dimethicone, and mixtures thereof. Emollients may be useful to prevent stratum corneum dehydration occurring due to the use of anhydrous solvents in the formulation. Examples of organic bases include 2-amino-2-methyl propanol, niacinamide, methanolamines, triethanolamines, Trisamino, AMP-95, AmP-Ultra PC 2000, triisopropanolamine, diisopropanolamine, Neutrol TE, Ethomeen, and mixtures thereof. The organic base may render the pH of the medicament basic or neutral, and may directly affect the release of NO from the diazeniumdiolate groups by slowing donor decomposition with increasing alkalinity.

Other exemplary excipients include water-soluble porogens. A water-soluble porogen is an additive that may facilitate water uptake and diffusion into the gel. Any suitable porogen may be used, but in some embodiments, the porogen may include sodium chloride, potassium chloride, sucrose, glucose, lactose, sorbitol, xylitol, polyethylene glycol, polyvinylpyrrollidone, polyvinyl alcohol or mixtures thereof. Electrolytes, like KCl, may also be added as excipients to enhance the stability of diazeniumdiolate NO donors.

Polymers may also act as excipients in topical gels. Exemplary polymers include hydrophilic polyurethanes, hydrophilic polyacrylates, co-polymers of carboxymethylcellulose and acrylic acid, N-vinylpyrrolidone, poly(hydroxy acids), polyanhydrides, polyorthoesters, polyamides, polycarbonates, polyalkylenes (e.g., polyethylene and polypropylene), polyalkylene glycols (e.g., poly(ethylene glycol)), polyalkylene oxides (e.g., polyethylene oxide), polyalkylene terephthalates (e.g., polyethylene terephthalate), polyvinyl alcohols, polyvinyl ethers, polylvinyl esters, polyvinyl halides (e.g., poly(vinyl chloride)), polyvinylpyrrolidone, polysiloxanes, polyvinyl acetates), polystyrenes, polyurethane copolymers, cellulose, derivatized celluloses, alginates, poly(acrylic acid), poly(acrylic acid) derivatives, acrylic acid copolymers, methacrylic acid, methacrylic acid derivatives, methacrylic acid copolymers, poly(butyric acid), poly(valeric acid), poly(lactide-co-caprolactone), copolymers thereof and blends thereof.

In some embodiments of the invention, the polymers may be superabsorbent polymers (SAPs). A polymer is considered superabsorbent, as defined per IUPAC, as a polymer that can absorb and retain extremely large amounts of water relative to its own mass. SAPs may absorb water up to 500 times their own weight and may swell up to 1000-times their original volume. Particular SAPs of interest include sodium polyacrylate, the polyurethane Tecophilic TG-2000, and polymers prepared by the use of polyacrylamide copolymer, ethylene maleic anhydride copolymer, cross-linked carboxy-methyl-cellulose, polyvinyl alcohol copolymers, polyvinylpyrrolindone and cross-linked polyethylene oxide. In some embodiments, the SAP may absorb water from the wound bed, thereby causing NO to release from the diazeniumdiolate-functionalized polysilane macromolecules.

In some embodiments of the invention, polymers that are relatively hydrophobic may be used. Any suitable hydrophobic polymer may be used. However, exemplary polymers that are relatively hydrophobic include aromatic polyurethanes, silicone rubber, polysiloxanes, polycaprolactone, polycarbonate, polyvinylchloride, polyethylene, poly-L-lactide, poly-DL-glycolide, polyetheretherketone (PEEK), polyamide, polyimide and polyvinyl acetate. In addition, a hydrophobic gel-base and/or rheology modifier may be used.

In some embodiments of the invention, the polymers may act as thickening agents in the medicaments. Specifically, the polymeric portion of the gel may act as a visco-elastic substance and may retain the gel at the site of application, along with the diazeniumdiolate-functionalized polysilane macromolecules dispersed therein.

In some other embodiments, a gel that includes a polymer may have spreadability such that it forms a thin film when applied on the skin surface. This film may enable the application of the contained NO-releasing polysiloxane macromolecules over a wide area, and may serve to maintain the NO-releasing polysiloxane macromolecules on the affected area of the skin.

Other excipients may include various ionic or non-ionic compounds to maintain stability of the formulation, thereby protecting from the de-emulsification, settling, agglomeration or degradation of the formulation constituents that may reduce its therapeutic or aesthetic value.

Examples of ionic compounds may include salts such as sodium chloride, potassium chloride; cationic, anionic or zwitterionic surfactants such as sodium dodecyl sulfate (SDS), perfluorooctanoate (PFOA), perfluorooctanesulfonate (PFOS), ammonium lauryl sulfate (ALS), sodium lauryl ether sulfate (SLES), alkyl benzene sulfonate, cetyl trimethylammonium bromide (CTAB), cetylpyridinium chloride (CPC), polyethoxylated tallow amine (POEA), benzalkonium chloride (BAC), benzethonium chloride, dodecyl betaine, cocamidopropyl betaine and cocoamphoglycinate.

Examples of non-ionic compounds that may act as excipients include non-ionic surfactants such as Pluronic, Tween, AMP, and Brij family of surfactants; and surfactants derived from biological sources, e.g, natural or semi-synthetic surfactants, such as oleic acid, sorbitan trioleate, sorbitan monooleate, lecithin, cocamide MEA, cocamide DEA and cocamidopropyl betaine. Surfactants (both ionic and non-ionic) may reduce the interfacial surface energy and may facilitate spreading of the ointment or liquid over a wider area.

In some embodiments of the invention, solvent excipients may be used as a carrier vehicle for the NO-releasing macromolecules and other excipients. The polymer chains may interact with the solvent and undergo swelling to form a network that may impart visco-elastic properties to the medicament. In some embodiments of the medicament, the solvent may evaporate upon application, leaving a residual film of the polymer along with the entrapped NO-releasing macromolecules.

Exemplary solvent excipients that may be useful in hydrophilic formulations may include dimethyl isosorbide, propylene glycol, glycerol, isopropanol, ethanol, benzyl alcohol, ethylene glycol, polyethylene glycol, ethoxydiglycol or mixtures thereof. Exemplary solvent excipients that may be useful in hydrophobic formulations may include capric/caprylic triglycerides, isopropyl myristate, mineral oil, isododecane, isodecyl neopentanoate, butylene glycol, pentylene glycol, hexylene glycol, methoxypolyethyleneglycol, cyclopentasiloxane, cyclotetrasiloxane, dimethicone, caprylyl methicone or mixtures thereof. In some embodiments, the hydrophilic gel may be an alcoholic gel, wherein the gel has an alcohol content in a range of 20 to 90 weight percent, and in some cases, in a range of 60 to 85 weight percent.

In addition to the diazeniumdiolate-functionalized polysiloxane macromolecules and excipients, the topical gels may also include at least one additional therapeutic agent such as antimicrobial agents, anti-acne agents, anti-inflammatory agents, analgesic agents, anesthetic agents, antihistamine agents, antiseptic agents, immunosuppressants, antihemorrhagic agents, vasodilators, wound healing agents, anti-biofilm agents and mixtures thereof.

Examples of antimicrobial agents include penicillins and related drugs, carbapenems, cephalosporins and related drugs, erythromycin, aminoglycosides, bacitracin, gramicidin, mupirocin, chloramphenicol, thiamphenicol, fusidate sodium, lincomycin, clindamycin, macrolides, novobiocin, polymyxins, rifamycins, spectinomysin, tetracyclines, vanomycin, teicoplanin, streptogramins, anti-folate agents including sulfonamides, trimethoprim and its combinations and pyrimetliamine, synthetic antibacterials including nitrofurans, methenamine mandelate and methenamine hippurate, nitroimidazoles, quinolones, fluoroquinolones, isoniazid, ethambutol, pyrazinamide, para-aminosalicylic acid (PAS), cycloserine, capreomycin, ethionamide, prothionamide, thiacetazone, viomycin, eveminomycin, glycopeptide, glyclyclycline, ketolides, oxazolidinone; imipenen, amikacin, netilmicin, fosfomycin, gentamycin, ceftriaxone, Ziracin, Linezolid, Synercid, Aztreonam, and Metronidazole, Epiroprim, Sanfetrinem sodium, Biapenem, Dynemicin, Cefluprenam, Cefoselis, Sanfetrinem celexetil, Cefpirome, Mersacidin, Rifalazil, Kosan, Lenapenem, Veneprim, Sulopenem, ritipenam acoxyl, Cyclothialidine, micacocidin A, carumonam, Cefozopran and Cefetamet pivoxil.

Examples of topical anti-acne agents include adapalene, azelaic acid, benzoyl peroxide, clindamycin and clindamycin phosphate, doxycycline, erythromycin, keratolytics such as salicylic acid and retinoic acid (Retin-A″), norgestimate, organic peroxides, retinoids such as isotretinoin and tretinoin, sulfacetamide sodium, and tazarotene. Particular anti-acne agents include adapalene, azelaic acid, benzoyl peroxide, clindamycin (e.g., clindamycin phosphate), doxycycline (e.g., doxycycline monohydrate), erythromycin, isotretinoin, norgestimate, sulfacetamide sodium, tazarotene, etretinate and acetretin.

Examples of antihistamine agents include diphenhydramine hydrochloride, diphenhydramine salicylate, diphenhydramine, chlorpheniramine hydrochloride, chlorpheniramine maleate isothipendyl hydrochloride, tripelennamine hydrochloride, promethazine hydrochloride, methdilazine hydrochloride, and the like. Examples of local anesthetic agents include dibucaine hydrochloride, dibucaine, lidocaine hydrochloride, lidocaine, benzocaine, p-buthylaminobenzoic acid 2-(die-ethylamino) ethyl ester hydrochloride, procaine hydrochloride, tetracaine, tetracaine hydrochloride, chloroprocaine hydrochloride, oxyprocaine hydrochloride, mepivacaine, cocaine hydrochloride, piperocaine hydrochloride, dyclonine and dyclonine hydrochloride.

Examples of antiseptic agents include alcohols, quaternary ammonium compounds, boric acid, chlorhexidine and chlorhexidine derivatives, iodine, phenols, terpenes, bactericides, disinfectants including thimerosal, phenol, thymol, benzalkonium chloride, benzethonium chloride, chlorhexidine, povidone iode, cetylpyridinium chloride, eugenol and trimethylammonium bromide.

Examples of anti-inflammatory agents include nonsteroidal anti-inflammatory agents (NSAIDs); propionic acid derivatives such as ibuprofen and naproxen; acetic acid derivatives such as indomethacin; enolic acid derivatives such as meloxicam, acetaminophen; methyl salicylate; monoglycol salicylate; aspirin; mefenamic acid; flufenamic acid; indomethacin; diclofenac; alclofenac; diclofenac sodium; ibuprofen; ketoprofen; naproxen; pranoprofen; fenoprofen; sulindac; fenclofenac; clidanac; flurbiprofen; fentiazac; bufexamac; piroxicam; phenylbutazone; oxyphenbutazone; clofezone; pentazocine; mepirizole; tiaramide hydrochloride; steroids such as clobetasol propionate, bethamethasone dipropionate, halbetasol proprionate, diflorasone diacetate, fluocinonide, halcinonide, amcinonide, desoximetasone, triamcinolone acetonide, mometasone furoate, fluticasone proprionate, betamethasone diproprionate, triamcinolone acetonide, fluticasone propionate, desonide, fluocinolone acetonide, hydrocortisone vlaerate, prednicarbate, triamcinolone acetonide, fluocinolone acetonide, hydrocortisone and others known in the art, predonisolone, dexamethasone, fluocinolone acetonide, hydrocortisone acetate, predonisolone acetate, methylpredonisolone, dexamethasone acetate, betamethasone, betamethasone valerate, flumetasone, fluorometholone, beclomethasone diproprionate, fluocinonide, topical corticosteroids, and may be one of the lower potency corticosteroids such as hydrocortisone, hydrocortisone-21-monoesters (e.g., hydrocortisone-21-acetate, hydrocortisone-21-butyrate, hydrocortisone-21-propionate, hydrocortisone-21-valerate, etc.), hydrocortisone-17,21-diesters (e.g., hydrocortisone-17,21-diacetate, hydrocortisone-17-acetate-21-butyrate, hydrocortisone-17,21-dibutyrate, etc.), alclometasone, dexamethasone, flumethasone, prednisolone, or methylprednisolone, or may be a higher potency corticosteroid such as clobetasol propionate, betamethasone benzoate, betamethasone dipropionate, diflorasone diacetate, fluocinonide, mometasone furoate, triamcinolone acetonide.

Examples of analgesic agents include alfentanil, benzocaine, buprenorphine, butorphanol, butamben, capsaicin, clonidine, codeine, dibucaine, enkephalin, fentanyl, hydrocodone, hydromorphone, indomethacin, lidocaine, levorphanol, meperidine, methadone, morphine, nicomorphine, opium, oxybuprocaine, oxycodone, oxymorphone, pentazocine, pramoxine, proparacaine, propoxyphene, proxymetacaine, sufentanil, tetracaine and tramadol.

Examples of anesthetic agents include alcohols such as phenol; benzyl benzoate; calamine; chloroxylenol; dyclonine; ketamine; menthol; pramoxine; resorcinol; troclosan; procaine drugs such as benzocaine, bupivacaine, chloroprocaine; cinchocaine; cocaine; dexivacaine; diamocaine; dibucaine; etidocaine; hexylcaine; levobupivacaine; lidocaine; mepivacaine; oxethazaine; prilocalne; procaine; proparacaine; propoxycaine; pyrrocaine; risocaine; rodocaine; ropivacaine; tetracaine; and derivatives, such as pharmaceutically acceptable salts and esters including bupivacaine HCl, chloroprocaine HCl, diamocaine cyclamate, dibucaine HCl, dyclonine HCl, etidocaine HCl, levobupivacaine HCl, lidocaine HCl, mepivacaine HCl, pramoxine HCl, prilocaine HCl, procaine HCl, proparacaine HCl, propoxycaine HCl, ropivacaine HCl, and tetracaine HCl.

Examples of antihemorrhagic agents include thrombin, phytonadione, protamine sulfate, aminocaproic acid, tranexamic acid, carbazochrome, carbaxochrome sodium sulfanate, rutin and hesperidin.

In addition to the diazeniumdiolate-functionalized polysiloxane macromolecules, excipients, and other therapeutic agents, the gels may also include other compounds that improve the organoleptic properties of the medicament. Examples of such compounds include perfumes, dyes and colorants; chelating agents including but not limited to EDTA, EGTA, CP94, citric acid; preservatives including but not limited to quaternary ammonium compounds, such as benzalkonium chloride, benzethonium chloride, cetrimide, dequalinium chloride, and cetylpyridinium chloride; mercurial agents, such as phenylmercuric nitrate, phenylmercuric acetate, and thimerosal; alcoholic agents, for example, chlorobutanol, phenylethyl alcohol, and benzyl alcohol; antibacterial esters, for example, esters of parahydroxybenzoic acid; and other anti-microbial agents such as chlorhexidine, chlorocresol, benzoic acid and polymyxin.

Tailoring Gels for Particular Therapeutic Uses

Wound healing occurs in several different phases, and may take place over 0-12 (or more) months. Wound healing phases include:

(i) Clotting

(ii) Cell Proliferation

(iii) Granulation Tissue Formation

(iv) Epithelialization

(v) Neovascularization or angiogenesis

(vi) Wound Contraction

(vii) Matrix deposition including collagen synthesis

(viii) Tissue Remodeling, including scar formation and scar remodeling

Nitric oxide may play a role in wound healing by a number of different mechanisms. First, extended exposure to low concentrations of nitric oxide may promote wound healing whereby nitric oxide acts as a signaling molecule in a number of wound healing cascades. Additionally, nitric oxide may also play a role in mitigating inflammation following injury. Modulation of inflammatory cytokines and cells of the inflammatory response via nitric oxide may significantly alter the wound healing phases above. Additionally, wound complications and pain may be significantly reduced with topical administration of nitric oxide as an anti-inflammatory agent. Furthermore, nitric oxide may act as a broad spectrum antimicrobial agent, particularly at relatively high concentrations. The antimicrobial effects of nitric oxide are broad ranging and different wound types may be colonized with different wound pathogens (e.g., gram negative bacteria, gram positive bacteria, fungus, etc.). Additionally, some pathogens may be more sensitive to nitric oxide than other pathogens. In some embodiments, nitric oxide may act as an antimicrobial agent by directly killing planktonic bacteria and other organisms; directly killing biofilm embedded bacteria and other organisms; indirectly killing microorganisms through nitrosative/oxidative stress; loosening biofilm matrix; increasing drug permeability across microbial membranes; and/or preventing recurrence of infection or biofilm formation.

Therefore, in some embodiments, the nitric oxide released from a particular medicament may provide a particular therapeutic action, such as act as a signaling molecule in a wound healing cascade, act as an anti-inflammatory agent and/or act as an antimicrobial agent. As such, the particular diazeniumdiolate-functionalized polysiloxane macromolecules and the composition of the gel may be tailored to provide the appropriate NO-release profile. Diazeniumdiolates may be triggered to release nitric oxide by exposure to water or another proton source, and an O²-protected diazeniumdiolate may be triggered to release nitric oxide by exposure to light, enzymatic action and/or pH adjustment.

Properties that may be tuned via the pharmaceutically acceptable carrier chosen include hydrophilicity and water uptake. The equilibrium moisture retention for a polymer can vary from 5 percent for certain aliphatic polymers to over 2000 percent for hydrogels and superabsorbent polymers. Thus, in some embodiments, the medicament may include a polymer that has a low equilibrium moisture retention in a range of less than 1 percent to 20 percent. In some embodiments, the medicament may include a polymer that has a moderate equilibrium moisture retention in a range of 20 percent to 200 percent. Further, in some embodiments, the medicament may include a polymer that has a high equilibrium moisture retention of 200 percent or higher. Other excipients may also absorb water and/or be hydrophilic or hydrophobic. In some embodiments, the gel may also include highly water absorbent excipients (e.g., an SAP, a humectant and/or glycerol) if fast release of NO is desired. If slower release of NO is desired, the gel may be more hydrophobic.

For topical medicaments that are gels or include monomers that may form gels upon polymerization, the properties of the gel may be tailored to affect desired NO-release characteristics. Properties of the gel that may be tailored include:

(i) Moisture Vapor Transfer Rate (MVTR)

-   -   The MVTR may be tunable in the gel to match the requirements of         a water reactive NO-releasing macromolecule in a gel yet still         maintain adequate MVTR for the desired wound or injury area.         Gels that maintain a moist wound bed are termed as occlusive. An         optimum MVTR maintains a moist wound environment which activates         debriding enzymes and growth factors that promote wound healing.         Occlusive gels may also act as a barrier towards exogenous         microbes, thereby preventing infection. Occlusivity is defined         by a MVTR through the wound cover of below 840 g/m² per 24 hour         period.

(ii) Biodegradability/Bioabsorbability

-   -   Biodegradability refers to the property of the gel to break down         into smaller molecular weight components under physiological         conditions. Bioresorbability refers to the property by which the         wound dressing can break down into smaller molecular weight         segments and the segments are completely taken into the body         without any biological reaction.

(iii) Oxygen Permeability

-   -   Adequate oxygen level facilitates neovascularization, aids in         collagen synthesis, and may prevent or minimize microbial         infection of the wound. Due to damaged vasculature in wounds,         there may be a low oxygen tension in the wound bed, leading to         hypoxia and anaerobic metabolism that can delay the healing         process. Gels may be oxygen permeable so that the wound receives         adequate topical oxygen for healing.

(iv) Nitric Oxide Permeability

-   -   The gel may have adequate permeability towards nitric oxide such         that the nitric oxide generated by the NO-releasing         macromolecules is available to the wound bed at a desired         therapeutic rate. Hydrophilic materials typically have a lower         NO permeability towards nitric oxide as compared to hydrophobic         materials. The NO permeability of the gel may be matched to the         release kinetics of the NO-releasing macromolecule and the rate         of water uptake by the polymer, in order to provide for optimal         release of NO from the gel.

(v) Ability to Swell

-   -   The ability of the gel to swell without dissolution upon contact         with wound moisture is beneficial in highly exudating wounds.         The gel may serve to imbibe excess moisture that may otherwise         cause wound maceration and foul odor.

(vi) Biocompatibility

-   -   The gel may be biocompatible, non-toxic, and non-irritable.

(vii) Ionic Character

-   -   The ionic character of the gel may affect the surface energy and         biocompatibility of the gel. The ionic character of the gel can         be quantified by measurement of the zeta potential of the wound         dressing material under physiological conditions. Surfaces with         highly negative or highly positive zeta potential may be         undesirable as they may have an anti- or pro-coagulant effect on         the wound and may increase surface energy.

In some embodiments of the invention, at least one property of the gel and/or at least one property of the diazeniumdiolate-functionalized polysiloxane macromolecules may affect the moisture uptake/retention, the moisture vapor transfer rate (MVTR), oxygen permeability, NO permeability, biodegradability/bioabsorbability, biocompatibility and ionic character. The total quantity of nitric oxide stored in the macromolecules, the hydrophobicity/hydrophilicity of the macromolecules and the gel, and the biodegradability/bioresorbability of the macromolecules and the gel control the intrinsic pH, the equilibrium moisture uptake, and regulate diffusion of oxygen into the gel to modulate nitrosative intermediates or the appearance of nitrite/nitrate byproducts. The formation of a polymer gel may also entrap diazeniumdiolate-functionalized polysiloxane macromolecules and prevent or minimize their penetration into the wound bed.

In some embodiments of the invention, the gel is a hydrophobic and non-aqueous gel. The use of an anhydrous and hydrophobic gel may minimize or prevent the release of NO during storage of the formulation. The hydrophic, non-aqueous compositions may also allow for slower diffusion of water required to initiate diazeniumdiolate decomposition and subsequent release of NO to a wound. As such, the gel may be useful for the treatment of acute and/or chronic wounds.

In some embodiments of the invention, the hydrophobic, non-aqueous gel base may be a silicone gel. In particular embodiments, the silicone gel includes cyclomethicone at a concentration in a range of 5 to 30 weight percent and crosslinked polydimethylsiloxane at a concentration in a range of 65 to 85 weight percent. In other embodiments, the hydrophobic, non-aqueous gel base includes polyol at a concentration in a range of 67 to 76 weight percent; electrolyte at a concentration in a range of 0.1 to 2.5 weight percent; silicone polyol at a concentration in a range of 20 to 30 weight percent; and volatile silicone-based solvent at a concentration in a range of 2.5 to 13 weight percent. In other embodiments, the hydrophobic, non-aqueous gel base includes petrolatum at a concentration in a range of 60 to 70 weight percent; dimethiconol at a concentration in a range of 5 to 10 weight percent; and volatile silicone-based solvent.

Further, in other embodiments, the hydrophobic, non-aqueous gel base includes a silicone elastomer at a concentration in a range of 60 to 70 weight percent; and volatile organic solvent at a concentration in a range of 5 to 10 weight percent, and in other embodiments, the hydrophobic, non-aqueous gel base includes silicone elastomer at a concentration in a range of 70 to 80 weight percent; and volatile organic solvent at a concentration in a range of 15 to 20 weight percent.

In addition, in some embodiments, the resulting hydrophobic, non-aqueous gel containing diazeniumdiolate-functionalized polysiloxane macromolecules may have a MVTR below 840 g/m² per 24 hour period.

Any suitable polyol may be used in the compositions described herein. However, examples of polyols include 1,2-ethanediol, 1,3-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,5-pentanediol, 1,10-decanediol, 2-methyl-1,3-propanediol, 2-methyl-2-butyl-1,3-propanediol, 2,2-dimethyl-1,3-propanediol, 2,2-dimethyl-1,4-butanediol, 2-ethyl-2-butyl-1,3-propanediol, neopentyl glycol hydroxypivalate, diethylene glycol and triethylene glycol.

Any suitable electrolyte may be used. However, examples of electrolytes include sodium chloride, potassium chloride, calcium chloride, and magnesium chloride.

Any suitable silicone polyol may be used. However examples of silicone polyols include dimethicone copolyol, laurylmethicone copolyol, cetyldimethicone copolyol, SilSense® SW-12 dimethicone copolyol ester, SilSense® Copolyol-1 Silicone, Lambent waxes, PEG/PPG-4/12 dimethicone, Bis-PEG/PPG-20/20 dimethicone, PEG/PPG-20/6 dimethicone, PEG/PPG-14/4 dimethicone, and PEG/PPG-20/20 dimethicone.

Any suitable silicone-based solvent may be used. However, examples of silicone-based solvents include cyclomethicone and dimethicone.

Any suitable silicone elastomer may be used. However, examples of silicone elastomers include dimethicone crosspolymer, dimethicone/vinyl dimethicone crosspolymer, cyclopentasiloxane/dimethicone crosspolymer, cetearyl/dimethicone crosspolymer, Wacker Belsil RG-100, ST-Elastomer 10, and trimethylsiloxysilicate/timethiconol crosspolymer.

In some embodiments, the gel includes diazeniumdiolate-functionalized polysiloxane macromolecules, caprylic or capric triglyceride at a concentration in a range of 25 to 55 weight percent; fumed silica at a concentration in a range of 4 to 8 weight percent; cyclomethicone at a concentration in a range of 5 to 20 weight percent; optionally, isopropyl myristate at a concentration in a range of 10 to 85 weight percent; and optionally, mineral oil at a concentration in a range of 10 to 90 weight percent.

In some embodiments, the topical gel includes diazeniumdiolate-functionalized polysiloxane macromolecules and a hydrophilic gel base. In particular embodiments, the concentration of the diazeniumdiolate-functionalized polysiloxane macromolecules is in a range of 0.1 to 2 weight percent. Further, in particular embodiments, the gel includes diazeniumdiolate-functionalized polysiloxane macromolecules, an ethylcellulose polymer at a concentration in a range of 8 to 20 weight percent; and a fatty acid ester at a concentration in a range of 60 to 90 weight percent.

In some embodiments, the gel includes diazeniumdiolate-functionalized polysiloxane macromolecules, polyethylene glycol at a concentration in a range of 15 to 60 weight percent; and propylene glycol at a concentration in a range of 30 to 80 weight percent; crosslinked polyacrylic acid at a concentration in a range of 0.5 to 4.0 weight percent; optionally, 2-amino-2-methyl propanol at a concentration in a range of 0.05 to 0.15 weight percent; optionally, glycerin at a concentration in a range of 15 to 25 weight percent; and optionally, niacinamide at a concentration in a range of 0.25 to 1.25 weight percent.

In some embodiments, the gel includes diazeniumdiolate-functionalized polysiloxane macromolecules, benzyl alcohol at a concentration in a range of 10 to 30 weight percent; isopropyl alcohol at a concentration in a range of 30 to 75 weight percent; HPC at a concentration in a range of 0.75 to 2.5 weight percent; optionally, 2-amino-2-methyl propanol at a concentration in a range of 0.05 to 0.15 weight percent; optionally, trolamine at a concentration in a range of 0.1 to 1.5 weight percent; optionally, fumed silica at a concentration in a range of 1.0 to 7.0 weight percent; and optionally, niacinamide at a concentration in a range of 0.25 to 1.25 weight percent.

In some embodiments of the invention, the diazeniumdiolate-functionalized polysiloxane macromolecules in the hydrophilic gel may have an octanol/water partition coefficient in a range of −2 to 0. In some embodiments of the invention, the diazeniumdiolate-functionalized polysiloxane macromolecules in the hydrophobic, non-aqueous gel may have an octanol/water partition coefficient in a range of 0.1 to 7.

Methods of Treating Wounds and Skin Ailments

In some embodiments of the invention, provided are methods of treating a wound by applying a topical gel according to an embodiment of the invention. Such methods may be used in combination with any other known methods of wound treatment, including the application of other therapeutic agents, such as those that have anti-inflammatory, pain-relieving, immunosuppressant, vasodilating, wound healing and/or anti-biofilm forming properties. For the methods used herein, additional therapeutic agents and methods may be used prior to, concurrently with or after application with a gel according to embodiments of the invention. Gels according to embodiments of the invention may also be used in any combination with any wound dressings known to those of skill in the art.

In some embodiments of the invention, the topical gels provided herein may be used in conjunction with at least one agent that can disrupt biofilm macrostructure prior to or in conjunction with the application of a wound dressing. In some embodiments, the anti-biofilm agent may disrupt the extracellular matrix of the biofilm. Examples of anti-biofilm agents that may act in this manner include lactoferrin, periodate, xylitol, DNase, protease, an enzyme that degrades extracellular polysaccharides. In some embodiments of the invention, the formulation of the anti-biofilm agent is acidic to promote enzyme activity of the DNase (e.g., mammalian DNases such as DNase II) and the acidic conditions simultaneously may also enhance the rate NO release from diazeniumdiolate macromolecules. In some embodiments, the protease may include at least one of proteinase K, trypsin, Pectinex Ultra SP (PUS) and pancreatin. In some embodiments, enzymes that degrade extracellular polysaccharides may include N-acetylglucosaminidases (e.g., dispersin B).

In some embodiments of the invention, the anti-biofilm agent may act by affecting the transcriptional, translational and/or post-translational regulation of quorum-sensing genes or gene products in the infecting organism(s). For example, the anti-biofilm agents may include at least one of hamamelitannin, cyclic di-GMP and sublethal concentrations of nitric oxide.

The anti-biofilm agents may also act by other mechanisms. For example, the anti-biofilm agent may cause the infecting organism to transition from a sessile state to a metabolically active state. As another example, the anti-biofilm agent may act by causing the infecting organism(s) to transition from a non-motile state to a motile phenotype.

In some embodiments of the invention, the topical gels provided herein may be used in conjunction with a wound debridement procedure. For example, in some embodiments, wounds may first be treated with a debridement procedure; and then a gel according to an embodiment of the invention may be applied to the debrided wound. The medicaments according to embodiments of the invention may increase the rate of wound healing, decrease inflammation and/or exert and antimicrobial effect. The wound dressings according to embodiments of the invention may be used in conjunction with any suitable debridement procedure. For example, the debridement procedure may be selective or nonselective.

In some embodiments, the debridement procedure may include at least one of surgical, enzymatic, autolytic, sharp, mechanical and biological processes. Any suitable surgical method may be used, but in some embodiments, the surgical method involves a surgeon cutting away nonviable tissue in the wound. Any suitable enzymatic method may be used, but in some embodiments, the enzymatic method may involve the use of one or more proteases, their required cofactors, and optionally any enhancing agents, to digest the nonviable tissue in the wound. Exemplary proteases include trypsin, papain or other vegetable-derived proteases and collagenase. Any suitable autolytic method may be used, but in some embodiments, the autolytic method involves maintaining a moist wound environment in order to promote the breakdown of nonviable tissue by enzymes that are naturally produced by the body. Any suitable mechanical method may be used, but in some embodiments, the mechanical methods include wet-to-dry gauze, irrigation, pulsatile lavage, whirlpool therapy and/or low frequency ultrasound. Any suitable sharp method may be used, but in some embodiments, the sharp method involves cutting away nonviable tissue by qualified clinical staff (e.g. RN or nurse practitioner). Any suitable biological method may be used, but in some embodiments, the biological method involves the use of maggots which selectively digest the nonviable tissue in the wound. These debridement methods may be used alone or in combination.

After the wound is debrided, a topical gel according to an embodiment of the invention may be applied. Additional processes may be performed and therapeutic agents may be applied. For example, after wound debridement, an anti-biofilm agent may be applied to the wound prior to or in conjunction with the application of the topical gels provided herein. Exemplary anti-biofilm agents include acetylsalicylic acid (aspirin), cyclic di-GMP, lactoferrin, gallium, selenium, as described above. Other compounds, such as hamamelitannin (witch hazel extract), arginine and c-di-GMP, may also be applied.

The gels may be applied to a subject in any suitable manner, such as, for example, rubbing, spreading or placing the gel on the wound or a wound dressing to be in contact with the wound. In some embodiments, the topical gel may be administered to a wound via spray delivery. A non-aqueous delivery propellant may be used for water the sensitive diazeniumdiolate-functionalized polysiloxane macromolecules. Further, in some embodiments, particular components of the gels may be separated at some point prior to application of the medicament. For example, the diazeniumdiolate polysiloxane macromolecule may be stored separately from an aqueous component or propellant until application (e.g., via spraying or applying a gel). In some embodiments, the diazeniumdiolate polysiloxane macromolecule may be combined with an aqueous constituent prior to application of the diazeniumdiolate polysiloxane macromolecules, and in some embodiments, an aqueous constituent may be applied to the wound bed sequentially.

Gels according to some embodiments of the invention may also be used to treat burns. A major goal in the treatment of burns is resuscitation and increase of fluid levels because of the significant loss of water from the body when the barrier function of the skin is compromised. Topical nitric oxide formulations that enhance the barrier function of the skin can not only restore this critical function for maintaining patient vitality but also prevent the infection of burn wound patients as compromised barrier function also creates an easy route for microbial contamination and colonization.

Hydrophobic gels in particular may be advantageous to use in the treatment of burns. Hydrophobic, non-aqueous gels can create an occlusive environment over the burn wounds and so prevent desiccation and create a moist wound environment. In some embodiments, for the treatment of burns, the diazeniumdiolate-funcationalized polysiloxane macromolecules can be loaded in such a gel at different concentrations during different times during the healing process. For example, to prevent infection, a gel may be applied that has a NO loading in a range of 10 μmol NO/g gel to 1 mmol NO/g gel. During later phases of tissue remodeling, for example several weeks after injury, nitric oxide may be loaded at concentrations in a range of 1 nmol NO/g gel to 10 μmol NO/g gel to facilitate healing and matrix remodeling. The moist wound environment created by the occlusive hydrophobic gels enables the release of nitric oxide from the diazeniumdiolate-functionalized polysiloxane macromolecules which is otherwise unexpectedly stable at room temperature in a non-aqueous gel matrix. The diffusion of water throughout the gel matrix thus controls the rate of proton initiated diazeniumdiolate decomposition, favoring faster diazeniumdiolate polysiloxane macromolecular compositions, such as those that have aqueous half-lives in the range of 0.5 minutes to 10 minutes. A rapid NO-release profile for hydrophobic gel matrices may enable these levels of antimicrobial NO release. However, for sustained release of nitric oxide from the gel from hours to days, the hydrophobic matrix coupled with a slowly-degrading diazeniumdiolate-functionalized polysiloxane macromolecule may produce a unique NO-release signature that exhibits a flat release profile.

Gels according to embodiments of the invention may be used to treat acne. Lipophilic diazeniumdiolate-functionalized polysiloxane macromolecules may target the pilosebaceous gland and penetrate the sebum rich environment, for example, as a potential treatment for acne vulgaris. As described above, gels according to embodiments of the invention may include other therapeutic agents. In the case of the treatment of acne, the gels may include other anti-acne agents such as retenoids, such as those described herein. Furthermore, agents such as retenoids may be used in conjunction (prior, concurrently or after) with a gel according to an embodiment of the invention.

Gels according to embodiments of the invention may be used to treat other skin ailments, either via anti-microbial action, anti-inflammatory action, or by any other mechanism. For example, topical gels described herein may be used to treat other skin ailments such as impetigo, psoriasis, tinea pedis, onychomycosis and the like.

Subjects suitable to be treated with a gel according to an embodiment of the invention include, but are not limited to, avian and mammalian subjects. Mammals of the present invention include, but are not limited to, canines, felines, bovines, caprines, equines, ovines, porcines, rodents (e.g. rats and mice), lagomorphs, primates, humans, and the like, and mammals in utero. Any mammalian subject in need of being treated according to the present invention is suitable. Human subjects are preferred. Human subjects of both genders and at any stage of development (i.e., neonate, infant, juvenile, adolescent, adult) can be treated according to the present invention.

Illustrative avians according to the present invention include chickens, ducks, turkeys, geese, quail, pheasant, ratites (e.g., ostrich) and domesticated birds (e.g., parrots and canaries), and birds in ovo.

The invention can also be carried out on animal subjects, particularly mammalian subjects such as mice, rats, dogs, cats, livestock and horses for veterinary purposes, and for drug screening and drug development purposes.

EXAMPLES Example 1 Synthesis of NO-Releasing Macromolecules

FIG. 1 illustrates the covalent storage of nitric oxide on the aminosilane N-methylaminopropyltrimethoxysilane as a diazeniumdiolate NO donor, followed by co-condensation with a backbone alkoxysilane, tetraethoxysilane, to form Nitricil™ composition 70. Such a NO-releasing macromolecule may be incorporated into medicaments according to some embodiments of the invention.

Example 2 Efficacy of Nitricil™-70 Against Representative Gram-Positive and Gram-Negative Bacteria

The antimicrobial efficacy of Nitricil™-70 Dry Powder was assessed against representative multi-drug resistant Gram-positive (HA-MRSA, ATCC 33591, SCCmec Type III) and Gram-negative (P. aeruginosa, ATCC 15442) organisms using the ASTM E 2315 Test Method. Various concentrations of NJ070 particles were incubated, in duplicate, with P. aeruginosa (See FIG. 2A) or HA-MRSA (See FIG. 2B) at 37° C. in a 1:1000 dilution of Trypticase Soy Broth. At the indicated time points, an aliquot from each culture was serially diluted and plated to quantitate the viable colony forming units (CFU/ml) remaining.

Solid Nitricil™ 70 kills both P. aeruginosa and MRSA in a dose- and time-dependent manner, with 99.9 percent killing of P. aeruginosa achieved at earlier time points and lower concentrations than are required for HA-MRSA. These data suggest that Nitricil™ is active against both Gram-positive and Gram-negative bacteria, but may be effective against Gram-negative bacteria at lower doses.

Example 3 Efficacy of a Nitricil™ 70 Silicone-Based Gel in Full Thickness Excisional Wounds in a an Infected Rat Animal Model

A hydrophobic, non-aqueous NO-releasing gel was formulated using 75 percent Dimethicone/Vinyl Dimethicone Crosspolymer and ˜25 percent cyclomethicone co-solvent as a viscosity modifier. Nitricil™-70 at a weight of 24 mg (0.1% w/w final gel loading) or 240 mg (1.0% w/w final gel loading) was dispersed in 6 ml of the cyclomethicone and sonicated to provide a homogenous particle suspension based on the likeness of the silicone solvent and exterior of the co-condensed siloxane particles. The concentrations of the components are listed below in TABLE 1. The Nitricil™ suspension was then combined with dimethicone gel in a 1:3 ratio to provide the finished compositions for animal testing. Blank vehicle contained only dimethicone and cyclomethicone co-solvent absent of any NO-releasing macromolecules.

TABLE 1 Nitricil ™ 70 Dimethicone Cross Polymer Cyclomethicone 0.1% 75% 24.9% 1.0% 75% 24.0%

Two 2×2 cm full thickness excisional wounds were made on the back of male nude rats across a total of 36 animals broken down into the groups shown in TABLE 2.

TABLE 2 Wound Daily model Treat- Innoculation Model EU & EU & EU & EU & EU & # of generation ment with generation NX NX NX NX NX Group Animals Test Article Day 0 w/ TA pseudomonas Day 0 Day 1 Day 3 Day 5 Day 7 Day 9 Total A 8 Control Two 2 × 2 cm Daily Day (0) 8 0 2 2 2 2 8 B 8 Blank Vehicle on rat Daily Day (0) 8 0 2 2 2 2 8 C 8 0.1% Nitricil gel back Daily Day (0) 8 0 2 2 2 2 8 D 8 1.0% Nitricil gel Daily Day (0) 8 0 2 2 2 2 8 E 4 No Treatment Daily Day (0) 4 4 0 0 0 0 4 TOTAL 36 36 4 8 8 8 8 36 Balance 32 24 16 8 0 after each Euthanasia

Immediately following wounding, wounds were challenged with 100 μL of a 10⁷ innoculum of P. aeruginosa and covered with Bioclusive Transparent Dressings (Johnson and Johnson) for 24 h to grow mature P. aeruginosa biofilms. Treatment with 200 mg of Blank Gel, 0.1 weight percent, and 1.0 weight percent Nitricil™ loaded silicone gels commenced on Day 1 and was repeated once daily for the duration of the study. The occlusive thin film dressings were also replaced following each treatment. On Day 3, two animals from each group were euthanized and 8 mm punch biopsies were taken from the center of each wound, homogenized in sterile saline, and plated to determine the number of colonies per gram of tissue. Referring to FIG. 3, untreated control wounds and blank vehicle treated wounds exhibited 2.5×10⁸ and 9.0×10⁸ CFU/g tissue respectively. However, 0.1 percent Nitricil™ 70 loaded gel demonstrated a >99 percent reduction in the number of P. aeruginosa per g tissue with an average value of 1.37×10⁶ CFU/g tissue across the 4 samples taken. The 1.0 percent gel also showed a substantial reduction in comparison to controls at 6.84×10⁶ CFU/g tissue.

Wound photographs were taken at each topical gel application and prior to necropsy. Quantitative measurements of the wound area for each treatment group were performed using the scale bar provided in each photograph. The wound area (cm²) were measured for all wounds available and converted to percent Wound closure when compared to the initial wound area measured for each individual wound. The data for Day 3 and Day 9 are shown in FIG. 4.

On Day 3, the 0.1 percent Nitricil™ loaded silicone, gel showed a dramatic enhancement, nearly 25 percent greater wound closure in comparison to all of the other treatment groups. A series of images for all of the treatment groups from Day 0 (wounding) until the completion of the study at Day 9 are shown in FIG. 5.

Example 4 Other Hydrophobic Formulations (Prophetic) A: Silicone-Based Non-Aqueous Emulsion

-   -   Aqueous formulations containing Nitricil™ in form of a cream         that can be applied to the wound bed.     -   Prepared by blending Phase A, that includes a polyol such as         propylene glycol (67 weight percent to 76 weight %), an         electrolyte such as NaCl (0.5 weight %) and the active agent         Nitricil™ (1 weight % to 10 weight %) with Phase B, which         includes a silicone-based polyol such as dimethicone copolyol         (20 to 30 weight %) and a volatile silicone-based solvent such         as cyclomethicone (2.5 weight % to 10 weight %).     -   Electrolytes such as NaCl may be added to the formulations to         stabilize the emulsion.     -   Phase A and Phase B are heated separately at 80° C. under         nitrogen to preserve diazeniumdiolate NO donor stability and         blended together at 800 RPM using a paddle stirrer. Cooled and         stored at room temperature.

The formulation concentrations, shown in % (w/w), are provided in TABLE 3.

TABLE 3 Phase A Phase B Propylene Glycol NaCl Nitricil ™ Dimethicone coplyol Cyclomethicone 76% 0.5% 1% 20% 2.5%

B: Silicone-Based Ointment

-   -   Non-aqueous ointment based on traditional Petrolatum.     -   Includes a Petrolatum bulk (60% to 70%) in addition to         dimethiconol (Dimethicone Blend 20, 5% to 10%), in which         Nitricil™ has been blended (1% to 10%); a volatile silicone         solvent, such as cyclomethicone, is used for viscosity         adjustment (10% to 20%).     -   Dimethicone Blend 20 provides ease of spreading and also may         provide a smooth skin-feel.     -   Under continuous agitation, disperse Nitricil™ in cyclomethicone         at room temperature; add Dimethicone Blend 20 at room         temperature, followed by addition of Petrolatum heated         separately to 75° C.

The formulation concentrations, shown in % (w/w), are provided in TABLE 4.

TABLE 4 Phase B Petrolatum Dimethicone Blend 20 Cyclomethicone Nitricil ™ 65% 5% 20% 10%

C: ST-Elastomer Based Non-Aqueous Gel

-   -   Non-aqueous gel including a silicone elastomer (70% to 80%)         blended with a volatile organic solvent (15% to 20%) containing         Nitricil™ (1% to 10%).     -   May contain isopropyl myristate as emollient (0.5% to 1%).     -   Dissolve isopropyl myristate in cylomethicone, disperse         Nitricil™, add ST-Elastomer 10 under continuous blending.

The formulation concentrations, shown in % (w/w), are provided in TABLE 5.

TABLE 5 Isopropyl Nitricil ™ ST-Cyclomethicone 5 ST-Elastomer 10 Myristate 5% 19% 75% 1%

D: Wacker Belsil-Based Non-Aqueous Gel

-   -   Non-aqueous gel containing Nitricil™ (1% to 10%), silicone         elastomer, Wacker Belsil RG-100 (60% to 80%), blended with a         volatile silicone organic solvent (15% to 25%) for viscosity         control.     -   Contains glycerol as emollient (1% to 2%).     -   Dissolve glycerol in cylomethicone, disperse Nitricil™, add         ST-Elastomer 10 under continuous blending.

The formulation concentrations, shown in % (w/w), are provided in TABLE 6.

TABLE 6 Nitricil ™ ST-Cyclomethicone 5 Wacker Belsil RG-100 Glycerol 2% 18% 78% 2%

Example 5 Antimicrobial Activity of a Nitricil™ 70 Based Hydrophilic Gel Against MRSA Biofilms

A hydrophilic, NO-releasing gel was formulated using glycerol as the base. Carbopol 940 was used as rheology modifier. Briefly, Carbopol 940 was dissolved in glycerol at a concentration of 0.5% (w/v) by overnight stirring of 0.1 g Carbopol 940 in 20 ml glycerol at 50° C. In a separate container, 200 μl of triethanolamine was added to 10 ml glycerol, to adjust the pH to 11.0.

Nitricil™-70 at a weight of 18.93 mg (1% w/w final gel loading) or 189.3 mg (10% w/w final gel loading) was dispersed in 1 ml of the glycerol at pH 11.0, using a paddle stirrer at 500 RPM. A half milliliter of the 0.5% Carbopol 940 solution was added to the Nitricil™-70 dispersion under continuous, agitation at 500 RPM. The resulting viscous gel was transferred to a 3 ml polypropylene syringe. The pH of the gel was measured to be 7.0.

The formulation concentrations, shown in % (w/w), are provided in TABLE 7

TABLE 7 Nitricil Carbopol 940/941 Glycerol  1% 0.13% 98.87% 10% 0.13% 89.87%

The NO-release of the gel was measured by weighing a small amount of the gel (2.8 mg) into the Chemiluminescent Nitric Oxide Analyzer, as shown in FIG. 6.

MRSA colony biofilms were grown on UV-sterilized 25 mm polycarbonate filters (0.22 μm) as described previously (Anderl et al 2000, Rani et al 2007). Briefly, an overnight culture of S. aureus ATCC 33591 was diluted to OD₆₀₀ of approximately 0.1. Ten microliters of the diluted culture was spotted in the center of a polycarbonate filter resting on a tryptic soy agar plate. Biofilms were grown for two days at 37° C., with a transfer to a new TSA plate after 24 h. At the initiation of the experiment, each filter was transferred to an individual well in a 6-well plate. Gel formulations (0.1 ml) were added drop-wise over top of each biofilm (three biofilms per treatment) without disrupting the biofilm structure. Plates were incubated inside at humidified box (37° C., 24 h). After 24 h, Letheen broth (1 ml) was used to wash each well and then added, along with each filter, to 9 ml of Letheen broth in a 50 ml conical. Conicals were sonicated (1 min) and vortexed (1 min). The resulting bacterial suspension was serially diluted and plated to obtain colony counts. The results are shown in TABLES 8 and 9.

TABLE 8 Raw Data for Nitricil ™ 70 Hydrophilic Gel versus MRSA biofilms Sample Id Rep Time CFU/ml Log CFU % Red Log Red No treatment 1 24 h 1.46E+09 9.16 −26.8 −0.12 No treatment 2 7.98E+08 8.90 30.6 0.15 No treatment 3 1.19E+09 9.08 −3.8 −0.03 HG-CONTROL-003 1 24 h 1.63E+08 8.21 85.8 0.84 HG-CONTROL-003 2 1.68E+08 8.23 85.4 0.82 HG-CONTROL-003 3 1.60E+08 8.20 86.1 0.84 01-00009-002-HG-01-0001 1 24 h 1.40E+06 6.15 99.88 2.90 01-00009-002-HG-01-0001 2 1.12E+06 6.05 99.90 3.00 01-00009-002-HG-01-0001 3 3.32E+06 6.52 99.7 2.53 01-00009-002-HG-10-0001 1 24 h 1.00E+03 3.00 99.99991 6.05 01-00009-002-HG-10-0001 2 1.00E+03 3.00 99.99991 6.05 01-00009-002-HG-10-0001 3 3.10E+03 3.49 99.9997 5.56

TABLE 9 Data Summary for Nitricil ™ 70 Hydrophilic Gel versus MRSA biofilms Average Test Article Time CFU/ml Log CFU % Red Log Red No treatment 24 h 1.15E+09 9.05 0.00 0.00 HG-CONTROL-003 24 h 1.64E+08 8.21 85.8 0.83 01-00009-002-HG- 24 h 1.95E+06 6.24 99.8 2.81 01-0001 01-00009-002-HG- 24 h 1.70E+03 3.16 99.9999 5.88 10-0001

Example 6 Other Hydrophilic Formulations (Prophetic) A: Ethocel Based Non-Aqueous Gel

-   -   Non-aqueous gel including ethylcellulose polymers dissolved in         propylene glycol dicaprylate/dicaprate (Miglyol).     -   The ethylcellulose polymers are used as pharmaceutical         excipients, tablet binders, etc. and Miglyol solvent has         inherent emollient properties due to its plant triglyceride         base.     -   The polymers Ethocel Std 7 FP Premium (11-16%), Ethocel Std 10         FP Premium (11-16%), Ethocel Std 100 FP Premium (7 to 12%) will         be used. These concentrations are lower for 100 FP due to its         longer chain length. Miglyol 840 solvent will be used (80% to         85%). Nitricil concentration will be varied from 1 to 10%.     -   Formulations with various Ethocel polymers are shown in TABLES         10-12.

TABLE 10 Ethocel Std 7 FP Premium Nitricil ™ Ethocel St 7 FP Miglyol 840 1% 16% 83% 2% 14% 84% 5% 12.5%   82.5%   10%  11% 79%

TABLE 11 Ethocel Std 10 FP Premium Nitricil ™ Ethocel St 10 FP Miglyol 840 1% 16% 83% 2% 14% 84% 5% 12.5%   82.5%   10%  11% 79%

TABLE 12 Ethocel Std 100 FP Premium Nitricil ™ Ethocel St 100 FP Miglyol 840 1% 12% 87% 2% 10% 88% 5% 8.5%  86.5%   10%   7% 83%

Example 7 Nitric Oxide Stability as a Function of Gel Excipients

A series of topical gels were formulated to contain nitric oxide-releasing silica particles in weight percentages ranging from 0.1% to 2.0% wt/wt and the percentage of nitric oxide recovered from the formulated gel prototypes was measured via nitric oxide chemiluminescence. Not all excipient combinations were able to maintain diazeniumdiolate NO-donor stability (TABLE 16). Unexpectedly, a series of topical gels containing diazeniumdiolate modified silica that exhibited stability at room temperature were discovered.

TABLE 13 Gels comprising Cab-O-Sil as the thickening agent (% wt/wt) Cab- Cyclo- Isopropyl O-Sil meth- Mineral PPG- ID Nitricil ™ CCTG myristate M5P icone Oil 15 A 0.1% 50.4% 42.0% 7.5% B 0.1% 7.5%   10% 82.4% C 1.0% 51.0% 42.0% 6.0% D 1.0% 6.0% 13.0% 80.0% E 1.0% 49.5% 42.0% 7.5% F 1.0% 7.5% 10.0% 82.5% G 1.0% 8.0% 10.0% 82.0% H 1.0%   29% 5.0% 49.0% 16.0% I 1.0%   29% 7.0% 47.0% 16.0% J 1.0%   52% 5.0%   13% 13.0% 16.0%

TABLE 14 Gels comprising Carbopol 980 as the thickening agent (% wt/wt) Propylene Carbopol ID Nitricil ™ PEG 300 glycol 980 Glycerin AMP Niacinamide K 0.1% 20.0% 62.1% 0.65% 17.0% 0.10% L 0.1% 76.0% 0.80% 23.0% 0.10% M 1.0% 57.1% 41.0% 0.80% 0.10% N 1.0% 56.8% 41.0%  1.0% 0.15% O 1.0% 55.7% 41.0%  1.0% 1.25%

TABLE 15 Alcohol based gels (% wt/wt) Benzyl Cab-O-Sil ID Nitricil ™ alcohol IPA HPC AMP Niacinamide Trolamine M5P P 2.0% 25.0% 71.0%  2.0% Q 2.0% 25.0% 69.0% 1.75% 1.25% 1.0% R 2.0% 25.0% 68.0%  1.0% 1.0% 3.0% S 2.0% 25.0% 71.1% 1.75% 0.1%

TABLE 16 % Nitric Oxide remaining in the Gel following initial formulation of excipients as a measure of stability performance (ND = not determined) % NO ID Remaining A ND B ND C 74% D 100% E 100% F 82% G 94% H 97% I 71% J 93% K ND L 15% M 83% N 54% O 59% P 70% Q 70% R 72% S ND

FIG. 7 shows NO-release curves showing change in kinetic profile as a function of excipients versus Nitricil alone. FIG. 8 shows the NO stability in gel over time decreases as a function of gel components. FIG. 9 shows the antimicrobial Time-kill of gels showing Nitricil vs. formulated hydrophobic gel at equivalent concentrations of silica prolonging release versus P. aeruginosa. FIG. 10 shows the hydrophilic vs. hydrophobic gel time kill efficacy against P. aeruginosa. FIG. 11 shows the does and time kill efficacy against P. acnes. FIG. 12 shows the dose and time kill efficacy against T. rubrum. 

1. A topical gel comprising diazeniumdiolate-functionalized polysiloxane macromolecules and a hydrophobic, non-aqueous gel base.
 2. The topical gel of claim 1, wherein the concentration of the diazeniumdiolate-functionalized polysiloxane macromolecules is in a range of 0.1 to 20 weight %.
 3. The topical gel of claim 1, wherein the hydrophobic, non-aqueous gel base is a silicone gel.
 4. The topical gel of claim 3, wherein the silicone gel comprises cyclomethicone at a concentration in a range of 5 to 30 weight % and crosslinked polydimethylsiloxane at a concentration in a range of 65 to 85 weight %.
 5. The topical gel of claim 3, wherein the hydrophobic, non-aqueous gel base comprises polyol at a concentration in a range of 67 to 76 weight %; electrolyte at a concentration in a range of 0.1 to 2.5 weight %; silicone polyol at a concentration in a range of 20 to 30 weight %; and volatile silicone-based solvent at a concentration in a range of 2.5 to 13 weight percent.
 6. The topical gel of claim 3, wherein the hydrophobic, non-aqueous gel base comprises petrolatum at a concentration in a range of 60 to 70 weight percent; dimethiconol at a concentration in a range of 5 to 10 weight percent; and volatile silicone-based solvent.
 7. The topical gel of claim 3, wherein the hydrophobic, non-aqueous gel base comprises silicone elastomer at a concentration in a range of 60 to 80 weight percent; and volatile organic solvent at a concentration in a range of 5 to 20 weight percent.
 8. The topical gel of claim 1, further comprising mineral oil at a concentration in a range of 10 to 90 weight percent; and fumed silica at a concentration in a range of 4 to 8 weight percent; cyclomethicone at a concentration in a range of 5 to 20 weight percent; optionally, isopropyl myristate at a concentration in a range of 10 to 85 weight percent; optionally, PPG-15 steryl ether at a concentration in a range of 5 to 16 percent; and optionally, caprylic or capric triglyceride at a concentration in a range of 25 to 55 weight percent.
 9. The topical gel of claim 1, wherein the diazeniumdiolate-functionalized polysiloxane macromolecules and gel excipients have an octanol/water partition coefficient in a range of 0.1 to
 7. 10. The topical gel of claim 1, wherein the diazeniumdiolate-functionalized polysiloxane macromolecules have a hydrodynamic radius in a range of 1000 nm to 10 microns.
 11. The topical gel of claim 1, wherein the diazeniumdiolate-functionalized polysiloxane macromolecules have a hydrodynamic radius in a range of 1 nm to 100 nm.
 12. The topical gel of claim 1, wherein the nitric oxide storage per gram is in a range of 0.1 pmol NO/g to 100 nmol/g gel.
 13. The topical gel of claim 1, wherein the nitric oxide storage per gram is in a range of 1 nmol NO/g to 10 μmol/g gel.
 14. The topical gel of claim 1, wherein the nitric oxide storage per gram is in a range of 10 μmol NO/g to 1 mmol/g gel.
 15. The topical gel of claim 1, further comprising an anti-acne agent, antimicrobial agent, benzoyl peroxide, or a corticosteroid.
 16. A topical gel comprising diazeniumdiolate-functionalized polysiloxane macromolecules and a hydrophilic gel base.
 17. The topical gel of claim 16, wherein the concentration of the diazeniumdiolate-functionalized polysiloxane macromolecules is in a range of 0.1 to 20 weight percent.
 18. The topical gel of claim 16, further comprising an ethylcellulose polymer at a concentration in a range of 8 to 20 weight percent; and a fatty acid ester at a concentration in a range of 60 to 90 weight percent.
 19. The topical gel of claim 16, further comprising polyethylene glycol at a concentration in a range of 15 to, 60 weight percent; and propylene glycol at a concentration in a range of 30 to 80 weight percent; crosslinked polyacrylic acid at a concentration in a range of 0.5 to 4.0 weight percent; optionally, 2-amino-2-methyl propanol at a concentration in a range of 0.05 to 0.15 weight percent; optionally, glycerin at a concentration in a range of 15 to 25 weight percent; and optionally, niacinamide at a concentration in a range of 0.25 to 1.25 weight percent.
 20. The topical gel of claim 16, further comprising benzyl alcohol at a concentration in a range of 10 to 30 weight percent; and isopropyl alcohol at a concentration in a range of 30 to 75 weight percent; HPC at a concentration in a range of 0.75 to 2.5 weight percent; optionally, 2-amino-2-methyl propanol at a concentration in a range of 0.05 to 0.15 weight percent; optionally, trolamine at a concentration in a range of 0.1 to 1.5 weight percent; optionally, fumed silica at a concentration in a range of 1.0 to 7.0 weight percent; and optionally, niacinamide at a concentration in a range of 0.25 to 1.25 weight percent.
 21. The topical gel of claim 16, wherein the diazeniumdiolate-functionalized polysiloxane macromolecules and the gel excipients have an octanol/water partition coefficient in a range of −2 to
 0. 22. The topical gel of claim 16, wherein the diazeniumdiolate-functionalized polysiloxane macromolecules have a hydrodynamic radius in a range of 1000 nm to 10 microns.
 23. The topical gel of claim 16, wherein the diazeniumdiolate-functionalized polysiloxane macromolecules have a hydrodynamic radius in a range of 1 nm to 100 nm.
 24. The topical gel of claim 16, wherein the nitric oxide storage per gram is in a range of 0.1 pmol NO/g to 100 nmol/g gel.
 25. The topical gel of claim 16, wherein the nitric oxide storage per gram is in a range of 1 nmol NO/g to 10 μmol/g gel.
 26. The topical gel of claim 16, wherein the nitric oxide storage per gram is in a range of 10 μmol NO/g to 1 mmol/g gel.
 27. The topical gel of claim 16, further comprising a retinoid, antimicrobial agent, benzoyl peroxide, or a corticosteroid.
 28. A method of treating a wound comprising applying the topical gel of claim
 1. 29. A method of treating a wound comprising applying the topical gel of claim
 16. 30. A method of treating a burn comprising applying the topical gel of claim
 1. 31. A method of treating acne comprising applying the topical gel of claim
 1. 32. A method of treating acne comprising applying the topical gel of claim
 16. 